2. Studying Density: Table Salt versus Salt Sense®

According to the label of the product, Salt Sense® contains real salt, but there is “33% less sodium per teaspoon.” How is this possible?

Prior to starting, answer the following questions:
What do you know about salt and its structure? How might the company achieve its claim of 33% less sodium per teaspoon? Is there 33% less chloride as well?

Materials:

Iodized Table Salt

Iodized Salt Sense® (Available in grocery stores and online)

Microscope or hand lens

Petri dishes or similar shallow, clear containers

Measuring beakers or graduated cylinders

Kitchen scale that can weigh grams

Laboratory notebook or paper

Pen for recording results

Procedure:

1. Place a small sample of table salt in one petri dish and a sample of Salt Sense® in a second petri dish. Look at the samples under the microscope.

Draw what you see for each sample. How might the differences you observe change the amount of sodium per teaspoon?

2. Calculate the density of each substance.

Density = mass/volume

where mass is the weight of the salt in grams and volume is the amount of salt in mL.

Tare a measuring beaker on the scale (ask the instructor or read the manual if you don’t know what “tare” means.)

Pour 20 mL of table salt in the beaker. Weigh the table salt in grams and record the weight.

Now tare the second beaker. Add 20 mL of Salt Sense® to the beaker and weigh it. Record the weight in grams.

Calculate the density of each sample. Which sample is less dense? How much less dense is it?

Usually on Wednesdays we feature Bug of the Week, so today's chemistry lesson is inspired by insects.

Dr. Thomas Eisner was a very curious man. He was particularly curious about insects, like the beetle shown in this video (has pop-up ad).

When he discovered these particular beetles, Dr. Eisner began to experiment with them because he wanted to know what and how they were squirting. One of the unexpected things he found out was that the temperature of the spray the beetle released was very hot, nearly 100° C. How could that be?

Endothermic and Exothermic Reactions

Sometimes chemical reactions between two or more substances give off or take in energy, often in the form of heat. In exothermic reactions, heat energy is given off during the reaction and the temperature increases. In endothermic reactions heat energy is removed by the reaction ("taken in") and the temperature of the reactants decreases.

Below are two chemical reactions that use household products. Find out whether they are exothermic or endothermic.

Notes: These activities are messy fun, so perform them in a sink, tub, or outdoors in an area where wet spills are not a problem. Also, scientists never eat or drink their experiments!

* Math alert: Originally I used Crystal Light pink lemonade mix, which came in 3.68 g packets (see the serving size information for the number of grams per packet). I used 7 packets for about 28 g. Then I switched to an off brand, and the packets were 2.6 g each (10 packets for 26 g). It worked just as well. Also, check the amount of vitamin C information on the labels. The raspberry-flavored lemonade mix contained significantly more citric acid for some reason.

Procedure 1:

Measure 100 mL (approx. 1/3 cup) of room temperature water and pour into in a container.

Add 26 g of drink mix into the water in the container. Stir until completely dissolved.

Use the thermometer or probe to measure the temperature of the solution, taking care not to rest the thermometer or probe on the bottom or side of the cup.

Measure 1/4 cup baking soda into the Styrofoam cup.

In a sink or similar area, quickly add the drink mix solution to the baking soda in the Styrofoam cup.

As the reaction starts to slow, take the temperature again. (You may want to let the children touch the solution and compare to the room temperature water. They will need to wash their hands afterwards.)

Did the temperature of the contents of the Styrofoam cup go up or down?

Reaction 2:

Materials:

2 teaspoons active yeast

Liquid measuring cup

Measuring teaspoon

Water at room temperature

Cup or similar container for mixing yeast

Large Styrofoam cup

Thermometer or temperature probe

Hydrogen peroxide (be sure to use 3 %, the kind sold for home use) - held at room temperature

Spoon

Procedure 2.

Measure 100 mL of room temperature water (approx. 1/3 cup) and pour into the yeast-mix container.

Mix the 2 teaspoons dry yeast into the water. Stir until thoroughly mixed.

Take the temperature of the solution, taking care not to rest the thermometer on the bottom or side of the cup.

Add 100 mL (about 1/3 cup) 3% hydrogen peroxide to the Styrofoam cup.

Take the temperature of the hydrogen peroxide, taking care not to rest the thermometer on the bottom or side of the cup. The two solutions should be roughly the same temperature.

In a sink or similar area, add the yeast solution to the hydrogen peroxide in the Styrofoam cup.

As the reaction starts to slow, take the temperature again. (You may want to let the children touch the solution and compare to the room temperature water. They will need to wash their hands afterwards.)

Did the temperature go down or up?

Which reaction was endothermic? Which reaction was exothermic? Let us know what you find out.

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If you are interested in learning more about the beetles, read the first chapter in:

Elements- Chemists have identified substances that can not be broken down further using chemical means. These are called the elements. Examples of elements are oxygen, carbon and gold. Jefferson Lab has a list of the 10 Most abundant elements in the universe.

Atoms- Atoms are the smallest units of elements. They are also what makes up all the matter in the universe.

Molecules- Many elements are found in nature as two or more atoms interacting together. When two or more atoms interact together or bond, then the result is called a molecule.

Atoms from different elements can also form molecules. An example of a molecule of this type is water, which is formed of hydrogen and oxygen atoms.

A friend used to ask me, “Has anyone ever seen an atom?” Recently scientists have developed technology that allows us to do just that. It is called an atomic force microscope/scanning tunneling microscope. They use extremely cold conditions to hold the atoms or molecules still enough to visualize. Want to see what they look like?

A Boy And His Atom: The World's Smallest Movie

This is a stop motion animated movie created using images from a scanning tunneling microscope. Note: This should really be called a boy and his molecule, because the researchers moved carbon monoxide (CO) molecules to create the images.

Moving Atoms: Making The World's Smallest Movie

In the video below you can see how researchers made A Boy and His Atom. You can also see how excited the researchers are to be doing this creative project and how it has practical applications. It is well worth watching.

Related activity:

Make An Element Collection

One great way to make chemistry more concrete is to have have experience with the pure form of different elements.

Caution: Some elements are gases at room temperature, and would be hard to hold in a collection. Some elements, such as mercury, beryllium, and arsenic, are toxic and should not be collected by children.